Former News of the World editor Andy Coulson has blamed lawyers for not telling him phone hacking was illegal in his court bid to avoid the harshest jail sentence.

Coulson, 46, faces up to two years in prison after he was found guilty last week of conspiring to intercept voicemails at the News of the World (NotW) following a marathon trial at the Old Bailey.

In mitigation, his lawyer Timothy Langdale QC said : "Despite the seriousness, the facts of the case do not justify the maximum penalty."

He said it was clear from the trial that Coulson was not alone in being ignorant of the fact that phone hacking was illegal.

"There are some features of this sorry affair which must be mentioned because they are capable of having, we submit should have, a mitigating effect on any sentence.

"Perhaps the most salient factor of the evidence is that no one at the NotW or the newspaper industry at large in 2000/06 realised that interception of voicemail messages was illegal, in the sense of criminal."

He said the NotW's own legal department, whom Coulson consulted frequently, never advised him that it was a crime.

Mr Langdale accepted that hacking was widespread when Coulson was editor between 2003 and 2006 but rejected the prosecution statement that the newspaper "became a thoroughly criminal enterprise" under Coulson's editorship.

After he left the NotW in 2007, Coulson went on to be a "trustworthy and straightforward" director of communications for David Cameron, he said.

The lawyer went on: "Because of his role after he left the NotW, because of the wider background to the wider investigation, Mr Coulson has become something of a lightning conductor for the political aspect."

He said the "media furore" in the first 24 hours after his conviction demonstrated this vividly but he maintained his client was still a "thoroughly decent" man.

Prosecutor Andrew Edis QC disputed Mr Langdale's assertion that Coulson was unaware of the illegality of phone hacking, saying the evidence could not be clearer - Coulson knew from the summer of 2004, around the time he heard of the David Blunkett voicemail to Kimberly Quinn.

The lawyer said: "He knew at least from that date that it was a criminal offence."

Mr Langdale replied: "I stand by everything that I said."

Immediately after Coulson's conviction, Prime Minister David Cameron issued a full and frank public apology for hiring him.

The shamed No 10 spin doctor, from Charing in Kent, will be sentenced on Friday alongside three of his former colleagues and private detective Glenn Mulcaire, who all admitted their part in the phone hacking plot last year.

The prosecution has also asked for £750,000 costs to be paid following the 139-day trial.

NotW news editor Greg Miskiw, 64, from Leeds; chief reporter Neville Thurlbeck, 52, of Esher, Surrey; and James Weatherup, 58, of Brentwood in Essex have all admitted one general count of conspiring together and with others to illegally access voicemails between October 2000 and August 2006.

Mulcaire, 43, from Sutton in south London, was first convicted of phone hacking with NotW royal reporter Clive Goodman in 2006 and served a prison sentence.

Following the renewed police investigation into the full extent of activities at the NotW, he admitted three more counts of conspiring to hack phones plus a fourth count of hacking the voicemail of murdered schoolgirl Milly Dowler in 2002 - an act which eventually led to the downfall of the NotW in 2011.

Coulson's co-defendants Rebekah Brooks and managing editor Stuart Kuttner denied any wrongdoing and were cleared of all charges.